1. Field of the Invention
The present invention generally relates to a fiber optic sensor device for measuring chromophoric compounds in biological fluid such as blood, saliva, sweat, etc.
2. Description of the Related Art
Approximately 60% of infants born in the United States each year become clinically jaundiced. Jaundice, or hyperbilirubinemia, results from increased production and transiently impaired elimination of bilirubin. While most affected neonates recover rapidly, some infants show persistently high levels of unconjugated bilirubin. The potential harms associated with moderate to severe jaundice include sensorineural hearing loss, bilirubin encephalopathy and kernicterus. Kernicterus is the most dreaded consequence of hyperbilirubinemia. When it occurs, it results in, for example, irreversible brain damage, choreoathetoid cerebral palsy, mental retardation, deafness, gaze paresis, and even death. Kernicterus survivors require lifetime care, at costs estimated to be about $22 to $40 million per child. If detected early, especially in high-risk cases, hyperbilirubinemia can be treated before kernicterus or less severe disorders develop. Some of the root causes of kernicterus cited by the American Academy of Pediatrics Subcommittee on Neonatal Hyperbilirubinemia include underestimating the severity of jaundice and delay in measurement.
Presently, there are two primary methods of measuring levels of bilirubin—serum blood tests and transcutaneous readings. Serum blood tests involve infant heel pricks while skin readings are a non-invasive method useful in low risk cases. Skin bilirubin levels are related to blood levels (i.e., the higher the blood level, the higher the skin level), but they may be difficult for the physician to assess visually with accuracy (perhaps the most common cause of underestimating the severity of jaundice). Additionally, there is a time lag between the real concentration in the blood and the coloration effect on the skin and the relationship is not linear. Therefore, skin tests are not ideal to monitor more severe cases where early detection increases the chance the infant will avoid irreversible consequences. Accordingly, there remains a need for an improved method and device for high-risk patients that allows for continuous, minimally invasive, real-time monitoring of bilirubin levels in either blood or amniotic fluid.
Status asthmaticus is a life threatening medical emergency in which asthma symptoms are not responsive to standard bronchodilator therapy. The prevalence of asthma has increased about 60% among all age groups over the last two decades. As of 2005, 0.5% to 2% of children with asthma were admitted to intensive care with status asthmaticus. However, asthma-related mortality has increased at an alarming rate (e.g., from 1993-1995, the overall annual age-adjusted death rate from asthma increased 40%). Treatment options for status asthmaticus remain limited and these patients are at risk for respiratory failure and mechanical ventilation. Once admitted to a hospital, patients with acute severe asthma are often treated with an intravenous infusion of theophylline. The therapeutic range for theophylline is 10 to 20 mg/l, but side effects begin to appear above 15 mg/l. Patients may already be taking oral theophylline, in which case the blood levels will not be known in advance of emergency treatment. The usefulness of theophylline is limited by its toxic effects, including neurotoxicity (e.g., seizures) and cardiac toxicity (e.g., dysrhythmias), that have adverse consequences for the patient, including death. There is no specific treatment for these toxic effects. Therefore, one must balance the life-saving efforts of the therapy with its possible toxic consequences. Accordingly, there remains a need for an improved method and device for measuring and continuously monitoring theophylline levels during therapy for a patient suffering from severe asthma such as status asthmaticus.